Orthogonal Frequency Division Multiple Access (OFDMA) modulation schemes have been proposed for downlink transmissions over an air interface in next generation communication systems such as 3GPP (Third Generation Partnership Project) E-UTRA (Evolved UMTS Terrestrial Radio Access), 3GPP2 Phase 2, and Worldwide Interoperability for Microwave Access (WiMAX) communication systems. In an OFDMA communication system, a frequency channel, or bandwidth, is split into multiple contiguous sub-bands, or Resource Blocks (RBs). Each sub-band comprises multiple, for example, 12 or 14, contiguous frequency sub-carriers that are orthogonal to each other. A grouping of multiple sub-bands, or RBs, comprises a sub-band group, or a Resource Block Group (RBG). A radio access network (RAN) then assigns the sub-bands to users' equipment (UEs) on a sub-frame basis, wherein a sub-frame may have, for example, a duration of one millisecond (ms).
In order to maximize bandwidth usage, OFDMA communication systems may engage in Frequency Diverse Scheduling (FDS) or narrowband scheduling. Narrowband scheduling is referred to as band-AMC within the 802.16 standard. Within narrowband scheduling, there are two ways of performing CQI reporting. In one method, called non-frequency selective CQI reporting, a user equipment (UE) is simply told which sub-band report on, and the UE reports on the CQI of that sub-band and is scheduled on that sub-band. In another approach, called frequency selective CQI reporting, a UE is instructed to measure a list of sub-bands and to report on the sub-bands with the best signal strength. Currently, frequency selective CQI reporting is not used in broadcast or multicast communication sessions (point-to-multipoint). However, wideband CQI reporting, wherein a UE reports an average CQI for an entire bandwidth, may not assure that a sub-band or sub-bands selected for the broadcast or multicast session will provide acceptable service to all participating UEs.
Therefore, a need exists for an improved method and apparatus for configuring CQI feedback in a broadcast or multicast OFDM communication session.
One of ordinary skill in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help improve understanding of various embodiments of the present invention. Also, common and well-understood elements that are useful or necessary in a commercially feasible embodiment are often not depicted in order to facilitate a less obstructed view of these various embodiments of the present invention.